Effect of Y(NO ₃ ) ₃ ·6H ₂ O addition on the structure and properties of micro-arc oxidation coatings on LA141 magnesium–lithium alloy

Magnesium–lithium (Mg–Li) alloys are the lightest structural metals with high specific strength, but their aerospace, defense, and 3C applications are limited by micro-galvanic corrosion from α-Mg/β-Li phase potential differences and by micropores/cracks in micro-arc oxidation (MAO) coatings that accelerate corrosive media penetration. To address these issues, this study introduces Y(NO 3 ) 3 ·6H 2 O as a functional additive in the MAO electrolyte for LA141 Mg–Li alloy (14 wt.% Li), aiming to improve coating densification and corrosion resistance. Unlike conventional rare-earth additives (Ce, La), Y(NO 3 ) 3 ·6H 2 O avoids forming insoluble silicates that reduce electrolyte conductivity. Orthogonal experiments determined optimal parameters: 10 g/L Na 2 SiO 3 , 5 A/dm 2 , 15% duty cycle, and 10 min oxidation. At 1.0 g/L Y(NO 3 ) 3 ·6H 2 O, the coating showed improved hardness (+244.88 HV), thickness (+10.0 μm), reduced roughness (0.736 μm) and porosity (7.23%), and a one-order decrease in corrosion current density with a 0.194 V positive shift in potential. XRD and SEM/EDS confirmed Y 3 + incorporation as Y 2 O 3 , which influenced plasma discharge, promoted MgO/Mg 2 SiO 4 formation, and suppressed micropores—an effect not reported in previous rare-earth-modified MAO coatings for high-Li alloys. This work demonstrates a scalable MAO route for LA141 with enhanced protective performance, and offers insights into Y(NO 3 ) 3 ·6H 2 O's role in coating formation on α/β dual-phase Mg–Li alloys. The approach could help balance coating compactness, mechanical strength, and corrosion resistance, supporting broader Mg–Li alloy use in demanding service environments.